This invention relates to digital noise blanking circuits, and more particularly to noise blanking circuits for eliminating from a signal false transitional pulses generated by noise while allowing one actual transitional pulse to pass.
In certain apparatus, for example tone decoders of the type described in U.S. patent application Ser. No. 641,453, filed Dec. 17, 1975, and assigned to the assignee of the instant application, it is necessary to detect the zero-axis crossing time of an analog input signal. Various means may be used to generate pulses representative of the zero-crossing time of the input signal. When noise appears on such input signal, however, additional false indications of transitions may occur, producing clusters of transitional pulses.